What is the significance of Schmorl's nodes in the lumbar spine?

Clinical Significance of Schmorl's Nodes in the Lumbar Spine

Schmorl's nodes in the lumbar spine are typically incidental findings without clinical significance, but they can occasionally cause acute back pain and rarely radiculopathy, and their presence is associated with intervertebral disc degeneration, particularly at upper lumbar levels.

What Are Schmorl's Nodes?

Schmorl's nodes represent herniation of nucleus pulposus through the cartilaginous and bony endplate into the adjacent vertebral body 1, 2. They are extremely common, with postmortem studies estimating prevalence exceeding 70% of the population 2. These lesions are most frequently found at the thoracolumbar junction 1.

Clinical Significance and Symptoms

Typically Asymptomatic

• Most Schmorl's nodes are incidental radiological findings discovered on imaging performed for other reasons 1, 3.
• In asymptomatic subjects, prevalence is approximately 11.5%, compared to 33.1% in patients with low back pain 4.

When They Cause Symptoms

• Acute painful Schmorl's nodes can occur, presenting with sudden onset of severe, localized back pain 5, 3.
• Patients with higher Schmorl's node scores have approximately 1.2-fold increased odds of experiencing low back pain 4.
• Radiculopathy from Schmorl's nodes is rare but documented, occurring when the node extends posteriorly through the vertebral body cortex into the epidural space, compressing nerve roots 2.

Association with Spinal Degeneration

Disc Degeneration Patterns

• At upper lumbar levels (L1-L2, L2-L3), patients with higher Schmorl's node scores have approximately 7-fold increased risk of severe intervertebral disc degeneration at corresponding levels 4.
• Lumbar Schmorl's nodes are frequently associated with disc degenerative disease 1.

Endplate Changes

• At lower lumbar levels (L4-L5), higher Schmorl's node scores are associated with Modic changes (vertebral endplate signal changes), with an odds ratio of 8.076 4.
• Higher Pfirrmann scores (disc degeneration grading) are also significantly associated with Modic changes at L4-L5, with an odds ratio of 2.696 4.

Risk Factors

Body weight is the most significant factor associated with Schmorl's node formation, with an odds ratio of 1.417 4. Other contributing factors include:

• Ethnic and gender influences 1
• Genetic background 1
• Biomechanical loading and impact stress on the lower spine (documented in horseback riding studies showing mechanical loading as a causative factor) 6

Diagnostic Imaging

MRI as the Gold Standard

• MRI is the imaging modality of choice for diagnosing Schmorl's nodes because it can detect edema, neovascularization, and extruded disc material 2.
• MRI is recommended as the neuroimaging study of choice for evaluation of patients with low back pain 6.

Acute vs. Chronic Nodes

• Acute symptomatic Schmorl's nodes demonstrate surrounding cortical edema and enhancement on MRI 2, 3.
• This distinguishes them from chronic, asymptomatic nodes and helps avoid confusion with bone metastases in malignancy contexts 1.

Imaging Indications

• Imaging should only be performed after 6 weeks of optimal conservative management in patients with subacute or chronic low back pain 7.
• Immediate MRI is appropriate if red flags are present: progressive neurologic deficit, cauda equina symptoms, suspected infection, known malignancy with new spinal pain, or trauma with neurologic symptoms 7.

Treatment Approach

Conservative Management First

• The mainstay of treatment for both asymptomatic and symptomatic Schmorl's nodes is conservative therapy 2.
• Conservative treatment should include physical therapy, medication trials, and activity modification for a minimum 6-week duration 7.

Interventional Options for Refractory Cases

• Percutaneous vertebroplasty (polymethylmethacrylate injection) can be considered for painful Schmorl's nodes refractory to medical or physical therapy 5.
• In one retrospective study of 23 patients, 18 reported improvement in back pain following vertebroplasty, with swift and persistent symptom reduction 5.

Surgical Consideration

• Surgical removal of disc material has been successful in cases of persistent radiculopathy from compression by a tunneling Schmorl's node 2.
• This is reserved for rare cases where conservative management fails and there is documented nerve root compression.

Clinical Pitfalls to Avoid

• Do not assume all Schmorl's nodes are symptomatic: The high prevalence in asymptomatic individuals means correlation with clinical presentation is essential 1, 2.
• Do not confuse new Schmorl's nodes with bone metastases in patients with known malignancy; MRI characteristics (edema pattern, enhancement) can help differentiate 1.
• Do not overlook the association with disc degeneration: When Schmorl's nodes are present, evaluate for concurrent intervertebral disc disease, particularly at upper lumbar levels 4.
• The most significant factor associated with low back pain intensity is severe disc degeneration at L5-S1, not Schmorl's nodes themselves 4.